The present invention relates to a disk apparatus with low power consumption.
A conventional disk apparatus, e.g., a floppy disk system is illustrated in FIG. 1. Floppy disk drivers 5 and 7 for driving the floppy disk drive are connected to a floppy disk controller 3 and a main processor 1 through a floppy disk interface (not shown). The controller 3 controls the drivers 5 and 7 under the control of the processor 1 to perform data read/write access, serial/parallel conversion and CRC (Cyclic Redundancy Check).
FIG. 2 is a detailed block diagram of a conventional floppy disk driver 5. The driver 5 has a magnetic head 9, a read/write amp 11 for supplying a read/write signal to the head 9, a stepping motor 13 for driving a carriage having the head 9 thereon, a stepping motor driver 15, a spindle motor 17 for driving the floppy disk, a spindle motor driver 19, a power supply controller 21, a power supply switching circuit 23 and a controller 25 for controlling the abovementioned components 11, 15, 19 and 21.
The controller 25 controls the overall operation of the driver 5 in response to an interface signal supplied from the controller 3. The controller 25 comprises a random logic circuit constituted by TTL gates or a microprocessor controlled by a program. The controller 25 is connected to the controller 21. The controller 21 is connected to the circuit 23. The controller 21 controls power supply switching of the circuit 23. The circuit 23 supplies a plurality of power supply voltages 27 externally supplied under the control of the controller 21 to or stops supplying them to the driver 15, the motor 13, the driver 19 and the motor 17. At the same time, the circuit 23 switches different types of power supply voltages (e.g., +5 V and +12 V). The circuit 23 supplies the power supply voltage to the driver 19 and the motor 17 or stops supplying it thereto. On the other hand, the circuit 23 supplies the power supply voltage to the driver 15 and the motor 13 or stops supplying it thereto, and switches the different types of power supply voltages applied to the driver 15 and the motor 13. The selection of the power supply voltage applied to the driver 15 and the motor 13 by the circuit 23 is performed such that a DC +12 V voltage is applied to the driver 15 and the motor 13 when the motor 13 requires a high torque, but a DC +5 V voltage is supplied thereto when the motor 13 requires a low torque. The amp 11 directly receives the externally applied power supply voltage.
In order to decrease power dissipation of the floppy disk driver 5 having the arrangement described above, the following implementation is utilized. A MOTORON signal is used as one of interface signals 29. Motor 17 may be controlled by the processor 1 directly in response to the MOTORON signal. Specifically, when the MOTORON signal is active (has a predetermined value), the controller 25 directly controls the controller 21, and the power supply voltage 27 is supplied from the circuit 23 to the driver 19 and the motor 17.
However, when the voltage level of the MOTORON signal is not active, the power supply voltage is not supplied from the circuit 23 to the driver 19 and the motor 17. In this manner, when the processor 1 does not use the driver 5, the power supply voltage is not supplied to the driver 19 and the motor 17, thereby achieving lower power dissipation and hence decreasing heat dissipation. The two types of power supply voltages are selectively applied to the motor 13 in accordance with the operating mode.
While the motor 13 is being operated, i.e., while a magnetic head seek is being performed, a high torque is required, so that the motor 13 receives a high voltage (i.e., 12 V). A period of time (generally called a "settling time") required for application of the high voltage is started when the head receives a seek instruction from the processor 1 and starts a seek operation (i.e., after a STEP PULSE as one of the interface signals is received) and is ended when the seek instruction is completely executed and the stepping motor is completely stopped.
When the motor 13 is stopped, i.e., when the head 9 is positioned above a predetermined track, a low voltage (+5 V) is applied to the motor 13 since a low torque is required in order not to cause a positioning error of the head 9.
When the processor 1 does not use the driver 5 and is held in the wait mode, the power supply voltage is not supplied to the driver 15 and the motor 13, thereby achieving low power consumption and decreasing heat generation.
FIGS. 3A through 3G are timing charts of signals for explaining the power consumption state of the driver 5. FIG. 3A shows a change in total power dissipation, FIG. 3B shows an application state of the external power supply voltage 27, FIG. 3C shows a state of the MOTORON signal, FIG. 3D shows a seek operation, FIG. 3E shows a state of the power supply voltage applied to the motor 13, FIG. 3F shows a state of power consumption in the motor 17, and FIG. 3G shows a state of the power supply voltage applied to the amp 11. As is apparent from FIGS. 3A through 3G, the power supply voltage 27 is always applied to the amp 11 irrespective of the operation mode of the driver 5, so that the amp 11 always consumes power and radiates heat. In particular, the voltage 27 is applied to the amp 11 when the motor 17 is started and while the seek operation is being performed. As a result, high power is consumed.